I designed a Mythical alchemist companion, using both HMRE and AA. Unfortunately, there are some inconsistencies between those books, both are from 2008, making it difficult to find out if one would have precedence over the others.
The issue?
HMRE has Lapis Maior (p81), with Base 5, +2 subst (requiring 3 paws of vis)
AA has Lapis Minor (p77), with Base5, +3 major.
One turn lead to gold, the other separates alloys and metal blend into their pure components (including gold if present).
Should the effect be swapped ? Separating alloys into its component looks like a substantial change, whereas turning lead into gold is a major change. At least, the relative level will be more consistent: 15 for purification, 20 for transformation.
Second question: the search for the philosopher's stone is not only about turning lead to gold, that's the physical, trivial achievement. The real goal is also the transformation of the alchemist, towards a form of immortality.
How would you tackle that - considering no Arts are involved ?
Theriacs granting similar effect than longevity potion ? (base 10, +1 to aging test per 2 extra levels ?)
a initiation granting some form of Immortality - is there a Mystery Cult ? is the research for Philosopher stone done in several steps, each step being a level of initiation ? what's the final outcome ?
Finally, a practical question for those who played alchemist: how to achieve high level (15+) with a philosopher's lab total ?
Did you note that Lapis Maior is a magical process (that also requires vis as you noted) and is not normally available to people doing experimental philosophy? This is fundamentally why the levels are showing up as they do. It's somewhat like comparing ReMe to Entrancement.
TMRE addresses the true immortality part through partly Hermetic means. You could design a similar, non-Hermetic cult using Mythic Alchemy.
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As for practical stuff:
Grab a whole bunch of books on Philosophiae. There are a lot available for not much money. You should be able to learn lots of formulas and get your score to 10+ this way.
Starting with Puissant/Affinity in Philosophiae is handy, as is Book Learner.
Also, choosing experimental philosophy as a specialty in Philosophiae is a good choice.
As you've got Mythic Alchemy, raise that some. But generally it's not as useful as Philosophiae.
As you've got Mythic Alchemy, work in a (Magic?) Aura.
Specialize your lab. The rules say you can use stuff from Covenants. I generally look for what gives a bonus to Muto or things that look particularly suited to alchemy, such as Cauldron and Still.
Let's assume you've read a bit, are using a decent Aura near your magi, and started with good Int. Ideally you have at least some of Puissant Philosophiae, Affinity with Philosophiae, and a specialty. Once you tune your lab, you can easily be looking at scores like Int 3 + Philosophiae 11 + Lab 11 + Mythic Alchemy 5 + Aura 4 = 34.
Then there is efficiency. For example, at that point, rather than making a level-20 thing, you might make a 10-dose size of it at level 25. You can do that in 3 seasons originally.
Your comment regarding magical transformation made me read again Mythic Alchemy and I found that Mythic Alchemy uses slightly different guidelines than Experimental philosophy - similar name, but different guidelines, which explains what I thought was discrepancy.
So I can still use Mythic Alchemy as a flat bonus while doing experimental philosophy, using the appropriate guidelines. Or I can do Mythic (magic) alchemy stuff, with different, slightly easier guidelines, but probably with some vis being required in the process.
Mythic Alchemy works both as a flat bonus as well as adding guidelines to experimental philosophy that are usually unavailable. (Even guidelines that can't even be permanent with Solomonic Alchemy.) The bonus applies to all the guidelines, both the non-magical and these new ones. Mythic Alchemy doesn't really change any guidelines that were already there, though. But getting to add Mythic Alchemy and Aura provide a huge boost, so it still helps a lot anyway.
On a related note, I have no idea why Cordovan Cuirbolli and similar use of preparing materials for craftsmen don't fall under standard experimental philosophy. It's not like boiled leather was never a real-world thing. I would, personally, put that level-2 guideline with experimental philosophy. The transmutation guidelines are clearly magical and are something most alchemists cannot do.
You can prepare materials for craftsmen using EP (Alchemical Steel is one such). The difference comes down to the effects and amount created.
EP produces small quantities of 'purified' or 'enhanced' material that has a special effect. The effect has to be clearly defined and you will often need multiple 'doses' for there to be a sufficient amount to produce larger things. It tends to be a difficult process.
MA works on a large volume of material (a whole season worth for a craftsmen) and reduces the target number for Superior/Excellent/Wondrous items. Its effect is to make fine work easier on the material including its ability to take minor enchantments and can make the material any color (including unnatural ones). It tends to be an easy process.
You can do both on the same material.
@David_Chart
And it looks like there is an error in HMRE. In the body on page 81 it says "The alchemist may prepare enough raw materials for a craftsman to use in one season (City & Guild, page 68)" while the example 'Cordovan Cuirbolli' has both +2 Size and only produces enough for 1 set of full leather armor. Looking at the Armor Table we see that "full suits" means Leather Scale since there is no full for Heavy Leather.
It should produce enough material for at least 4 sets of leather scale armor. The Size modifier makes no sense.
I understand that. But seriously, look at Cordovan Cuirbolli. Boiled leather is a real-world example, isn't it? I could totally understand Cordovan Cuirbolli being built (non-Mythic guideline) like Alchemical Steel. That would be fine. But it's built with this other guideline. So either this other guideline isn't really what you say, or Cordovan Cuirbolli is misplaced/misnamed.
In regards to "achieve alchemical immortality", a while ago I've done a Learned Magician Alchemist (of Soba) that found various Initiation Scripts for virtues similar to Hermetic Alchemy.
These virtues use the Learned Arts to achieve that, so not a plain mundane alchemist way
You can find the scripts and the virtues here, if you are curious: Link
Make a note somewhere. I'm not collecting errata at the moment — and, after the crowdfunding, there will need to be a discussion about what happens with that.